The apparatus shown between the vertical dashed lines in FIG. 1, and in more detail in FIG. 2 plus FIG. 3, typically is constructed as a separate unit for use with input and control apparatus as shown in the left hand part of FIG. 1 and for providing an output voltage to a controlled system as shown in the right hand part of FIG. 1. The unit, conveniently referred to herein either as a hybrid function generator or more simply as a ramp generator, is intended primarily for receiving successive input voltages and providing output voltages that become proportional thereto. In the embodiment of the function generator shown in the drawings the proportion is 1 to 1, so that the output voltages become equal to the input voltages.
The output voltages are provided in the same time sequence as the input voltages that are received; but instead of jumping instanteously from one voltage level to the next in stepwise fashion the output voltage increases or decreases in a continuous manner, approximately linearly with time, from each level to the next. Then it remains at that level until a new and different input voltage triggers it to provide a linear ramp to the next level as determined by the next input voltage.
The hybrid function generator typically is designed to receive its input voltages and control signals from a computer that comprises at least a central processing unit 46 connected as indicated at 47 to provide digital signals to a digital to analog converter 48 for providing as indicated at 49 an analog voltage input 11 having an amplitude that is determined by the digital signal at 47. The computer typically also comprises transistor-transistor logic or other suitable digital switching circuitry 36 that is actuated by digital logic signals from the central processing unit 46, as indicated at 67, and providing digital logic signals 36D, 36R, 36S, selectively, in response thereto.
The computer is programmed in any convenient manner, conventional or otherwise, to provide the appropriate input voltages 11 and control signals 36D, 36R, 36S at the appropriate times in accordance with the selected program and input data. The computer typically also comprises flag responsive digital logic circuitry 44 for receiving flag signals from the hybrid function generator, as is indicated at 43, and feeding digital logic signals to the central processing unit 46 in response thereto, as is indicated in 45. The computer program typically includes routine tests or other steps, or both, responsive at least in part to the flag signals at 45.
All of this in actual operation requires only a bare minimum of overhead time from the computer. In fact this is an important advantage of the present invention, which generates a stepless linear ramp output voltage from each desired level to the next with only this bare minimum of interaction with the computer.
In contrast, earlier typical known methods of generating an analog ramp voltage require substantially continuous operation of a computer to generate each ramp not as a truly continuous linear function of time but actually as an approximation thereof comprising a series of small steps, each actuated by a separate digital signal from the computer, all the way from each main step to the next. In other words as long as the ramp is being generated the computer is continuously busy counting up or down, jumping from point to point along the ramp. Typical appratus of this type is disclosed in U.S. Pat. No. 3,971,923 of Linder.
The present invention is quite versatile. Typical apparatus as shown in the drawings has been used to provide linear ramp voltages at rates as high as 100 cycles (excursions typically of 20 volts total from maximum positive voltage to maximum negative voltage, and then back) per second, and at rates as low as 25 seconds per cycle (about 2.4 cycles per minute). Even at high ramping rates, only a negligible amount of computer time is required. So even a fairly slow computer can be shared without perceptibly reducing the time available for other tasks.
The controlled system 50 may comprise virtually any type of apparatus (typically a servo system) that can be controlled at least in part by analog voltages. Where appropriate, the operation of the apparatus for a specific purpose may be controlled by a predetermined sequence of digital words specifiying the input voltages to be fed to the ramp generator. Or the operating program may include calculations by the computer of later input and rate controlling instructions based upon data from the controlled system 50 resulting from an earlier input or earlier inputs. For example, the computer might calculate the next input voltage on the basis of a quantitative effect produced in the controlled system by the preceding input.
Thus, the novel combination of circuitry and associated features in the present invention provides substantial advantages in greatly reduced costs of computer time, as well as greater convenience and other advantages that will be apparent from the disclosure herein.